Hyperspectral imaging is a technique used for surveillance and reconnaissance in military, geophysical and marine science applications. Objects viewed by a hyperspectral imaging system are often displayed in three-dimensions, x, y (spatial) and λ (color wavelength). Spatial observations (x, y) allow a person to observe an image when high contrast is available. However, during conditions of low contrast, such as fog, smoke, camouflage, and/or darkness, or when an object is too far away to resolve, spectral signatures help identify otherwise unobservable objects, for example to differentiate between friendly and enemy artillery.
The hyperspectral imaging technique typically employs a scanning slit spectrometer, although Fourier-transform imaging spectrometers (FTIS), and scanning filter (Fabry-Perot) imaging systems have also been used. These devices, however, record only two-dimensions of a three-dimensional data set at any one time. For example, the scanning slit spectrometer takes spectral information over a one-dimensional field of view (FOV) by imaging a scene onto a slit then passing that collimated image from the slit through a dispersive element (prism) and re-imaging various wavelength images of the slit onto a detector array. In order to develop three-dimensional information, the slit is scanned over the entire scene producing different images that must be positionally matched in post-processing. The FTIS and Fabry-Perot techniques also scan; the former scans in phase space, and the latter scans in frequency space.
Current scanning spectrometer designs have resulted in large, expensive and unwieldy devices that are unsuitable for hand-held or vehicle applications. While these spectrometers have been employed effectively in airborne and satellite applications, they have inherent design limitations. These limitations arise due to motion of the associated platform, motion or changes in the atmosphere, and/or motion of the objects in the image field that occur during scan sequences. Motion of the platform results in mismatched and misaligned sub-images, reducing the resolution and hence the effectiveness of the observations, while a moving object, such as a missile, may escape detection if the object is moving faster than the spectrometer scan rate.